This invention relates to apparatus for performing roll bending on shape metal, such as an angle bar, channel bar, etc., and more particularly it is concerned with an apparatus of the type described which enables shape metal of various shapes and dimensions to be bent by rolling.
Apparatus for performing bending of shape metal include tension bending apparatus, angle benders and roll bending apparatus, for example. In tension bending apparatus, shape metal of a required length is gripped at opposite ends and wound on a forming die of the required profile while imparting a tension thereto, so as to thereby bend the shape metal.
When bending operations are performed on shape metal by using this type of apparatus, it is necessary that at ension of a higher magnitude be imparted to the shape metal as the radius of curvature of the bend of the shape metal increases. Application of a tension of high magnitude produces a high degree of elongation in the shape metal, and since an outer edge portion of the shape metal undergoes elongation due to the bending working performed thereon, the outer edge portion can be ruptured or fall toward the form die, or the dimension of the shape metal in the radial direction can undergo great changes. When these troubles occur, it is impossible to bend the shape metal into a desired shape.
An angle bender comprises a rotatable base supporting a winding roll and a clamp jig, a working roll located in face-to-face relation to the base and the winding roll while being spaced apart therefrom by a distance corresponding to the thickness of the shape metal to be handled, and a guide roller for guiding and regulating the travel of the shape metal. In the angle bender of this construction, shape metal is inserted between the winding roll and the working roll along the guide roller and secured at one end to the base by means of the jig. As the base is rotated when the parts are in the aforesaid condition, the shape metal is wound on the winding roll because its travel is guided and regulated by the guide roller and the working roll, so that the shape metal can be bent as desired.
When bending is performed as described herein above, forces exerted on inner edge and outer edge portions of the shape metal might vary from each other when it is and buckling can occur in the inner edge portion of the shape metal. Thus, this bending apparatus suffers from the disadvantage of being unable to handle shape metal of thin thickness.
A roll bending apparatus is used for bending shape metal by rolling in such a manner that the thickness is successively reduced in going from the inner edge toward the outer edge when bending of the shape metal is accomplished. Such apparatus is disclosed in U.S. Pat. No. 3,388,449, for example.
This type of roll bending apparatus is capable of obtaining a bend of a relatively small diameter. However, it is disadvantageous in that limitations are placed on the shape and dimensions of the shape metal that can be handled, so that the usefulness of the apparatus is restricted.